Pistons

ABSTRACT

Pistons are disclosed herein. An example apparatus includes a piston defining a chamber and a circumferential groove in communication with the chamber. At least a portion of the chamber is to be substantially filled with a fluid. The example apparatus also includes a piston ring disposed in the chamber and the groove. The fluid is to apply a first pressure to the piston ring to enable the piston ring to apply a second pressure to a cylinder wall. The second pressure is to be greater than the first pressure.

FIELD OF THE DISCLOSURE

This disclosure relates generally to piston actuators and, moreparticularly, to pistons.

BACKGROUND

A piston actuator typically includes a piston disposed inside acylinder. The piston actuator may be single-acting or double-acting. Ifthe piston actuator is single-acting, the piton actuator may employfluid to drive the piston in one direction, and a spring may return thepiston to a fail-safe position such as, for example, a closed positionor an open position. If the piston actuator is double-acting, the pistonactuator may employ fluid to drive the piston in either of twodirections.

SUMMARY

Pistons are disclosed herein. An example apparatus includes a pistondefining a chamber and a circumferential groove in communication withthe chamber. At least a portion of the chamber is to be substantiallyfilled with a fluid. The example apparatus also includes a piston ringdisposed in the chamber and the groove. The fluid is to apply a firstpressure to the piston ring to enable the piston ring to apply a secondpressure to a cylinder wall. The second pressure is to be greater thanthe first pressure.

Another example apparatus disclosed herein includes a piston defining afluid chamber and a circumferential groove in communication with thefluid chamber. A first seal is disposed in the fluid chamber. A secondseal disposed in the groove and operatively coupled to the first seal.The first seal is to provide a fluid seal against the piston, and thesecond seal is to provide a fluid seal against a cylinder wall.

Another example apparatus disclosed herein includes a piston including afirst end portion spaced apart from a second end portion to define afluid chamber. The example apparatus also includes a piston ringdisposed between the first end portion and the second end portion of thepiston to define a first area in the fluid chamber and a second area inthe fluid chamber. The first area is to be substantially filled with afluid. A first portion of the piston ring is to form a fluid sealagainst the first end portion of the piston and the second end portionof the piston. A second portion of the piston ring is to form a fluidseal against a cylinder wall.

The features, functions and advantages that have been discussed can beachieved independently in various examples or may be combined in yetother examples further details of which can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example piston disclosed herein.

FIG. 2 is a cross-sectional view of the example piston of FIG. 1.

FIG. 3 is another cross-sectional view of the example piston of FIGS.1-2.

FIG. 4 is an enlarged, cross-sectional view of the example piston ofFIGS. 1-3.

FIG. 5 illustrates the example piston of FIGS. 1-4 in communication witha fluid reservoir.

Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like parts. As used in this disclosure, stating that any part (e.g.,a layer, film, area, or plate) is in any way positioned on (e.g.,positioned on, located on, disposed on, or formed on, etc.) anotherpart, means that the referenced part is either in contact with the otherpart, or that the referenced part is above the other part with one ormore intermediate part(s) located therebetween. Stating that any part isin contact with another part means that there is no intermediate partbetween the two parts.

DETAILED DESCRIPTION

Pistons are disclosed herein. An example piston disclosed herein maydefine a fluid chamber and a circumferential groove in communicationwith the fluid chamber. In some examples, a piston ring is disposedbetween two end portions of the piston. A first portion of the pistonring may be disposed in the fluid chamber, and a second portion of thepiston ring may be disposed in the groove. In some examples, the firstportion of the piston ring forms fluid seals against the two endportions of the piston to define a first area in the fluid chamber.Fluid in the first area of the fluid chamber may apply pressure to thefirst portion of the piston ring. As a result, the second portion of thepiston ring may apply a second pressure to a cylinder wall to form afluid seal against the cylinder wall. The second pressure may be greaterthan the first pressure. In some examples, a pressure differential isprovided across the first portion of the piston ring to enable the firstportion of the piston ring to transfer force to the second portion ofthe piston ring.

In some examples, the first portion of the piston ring is a firsto-ring, and the second portion of the piston ring is a second o-ring.The first o-ring may have a first cross-sectional size greater than asecond cross-sectional size of the second o-ring. In some examples, thefirst o-ring is in contact with the second o-ring to operatively couplethe first o-ring and the second o-ring.

FIG. 1 illustrates an example piston 100 disclosed herein. The examplepiston 100 may be disposed in a cylinder 302 (FIG. 3) of a single-actingactuator, a double-acting actuator, and/or any other type of pistonactuator to operate one or more devices such as, for example, a valve.The example piston 100 may be driven via any suitable fluid such as, forexample, oil, water, air, etc. disposed on a first side 102 of thepiston and/or a second side 104 of the piston.

The example piston 100 includes a first end portion 106 coupled to asecond end portion 108. In the illustrated example, a piston ring 110 isdisposed between the first end portion 106 and the second end portion108. During operation of the example piston 100, the piston ring 110forms a fluid seal against a wall 312 (FIG. 3) of the cylinder 302.Thus, the example piston ring 110 substantially prevents fluid fromflowing from the first side 102 of the piston 100 to the second side 104of the piston 100 and/or from the second side 104 of the piston 100 tothe first side 102 of the piston 100. Although the example piston 100 ofFIG. 1 includes one piston ring 110, other examples include othernumbers (e.g., 2, 3, 4, etc.) of piston rings.

FIG. 2 is a perspective, cross-sectional view of the example piston 100of FIG. 1. The example piston 100 defines a fluid chamber 200 and acircumferential groove 202 in communication with the fluid chamber 200.In the illustrated example, the first end portion 106 is spaced apartfrom the second end portion 108 via a spacer 204 to define the groove202 and the fluid chamber 200 between the first end portion 106 and thesecond end portion 108. The example spacer 204 is disposed inside thefluid chamber 200 and extends from the first end portion 106 to thesecond end portion 108. In other examples, the first end portion 106 maybe coupled to the second end portion 108 via a plurality of spacers, oneor more mechanical fasteners (e.g., bolts), and/or any other suitabletechnique.

FIG. 3 is another cross-sectional view of the example piston 100 ofFIGS. 1-2 employed in a double-acting actuator 300. The example piston100 is disposed in the cylinder 302. A first stem 304 is coupled to thefirst side 102 of the piston 100. A second stem 306 is coupled to thesecond side 104 of the piston 100. In other examples, the piston 100 maybe coupled to a single stem.

The example piston ring 110 includes a first portion 308 disposed in thefluid chamber 200 and a second portion 310 disposed in the groove 202adjacent the wall 312 of the cylinder 302. The first portion 308 of theexample piston ring 110 forms fluid seals against the first end portion106 and the second end portion 108 of the piston 100 to enable a firstarea 314 of the fluid chamber 200 to be substantially filled with afluid and pressurized via the fluid. As described in greater detailbelow, a first pressure of the fluid in the first area 314 applied tothe first portion 308 of the piston ring 110 enables the second portion310 of the piston ring 110 to form a fluid seal against the wall 312 ofthe cylinder 302. In the illustrated example, the first area 314 isdefined by the first end portion 106 of the piston 100, the second endportion 108 of the piston 100 and an inner diameter side 316 of thefirst portion 308 of the piston ring 110.

In some examples, fluid is flowed into the first area 314 of the fluidchamber 200 during operation of the actuator 300 to pressurize the firstarea 314. In the illustrated example, the first area 314 of the fluidchamber 200 receives fluid from within the cylinder 302 to fill thefirst area 314 with the fluid and/or pressurize the first area 314 tothe first pressure. The example first end portion 106 of the piston 100defines a first port 318 in fluid communication with the first area 314and the cylinder 302. The example second end portion 108 of the piston100 defines a second port 320 in fluid communication with the first area314 and the cylinder 302. A first check valve 322 is disposed in thefirst port 318, and a second check valve 324 is disposed in the secondport 320. In other examples, the piston 100 includes other numbers ofcheck valves (e.g., 1, 3, 4, etc.) in communication with the first area314 and the cylinder 302. In the illustrated example, the first checkvalve 322 and/or the second check valve 324 enables fluid to flow fromthe cylinder 302 into the first area 314 if the first pressure in thefirst area 314 is below a lower threshold pressure and/or if the fluidpressure in the cylinder 302 is above an upper threshold pressure. Thus,fluid pressures employed to drive the piston 100 may be used topressurize the first area 314 to enable the piston ring 110 to form thefluid seal against the wall 312 of the cylinder 302.

In some examples, the first area 314 of the fluid chamber 200 ispressurized prior to operation. The piston 100 may be pressurized priorto operation by substantially filling the first area 314 with fluidduring manufacture and/or assembly of the example piston 100. Once thepiston ring 110 is disposed between the first end portion 106 and thesecond end portion 108 of the piston 100 and the first area 314 ispressurized via the fluid, the piston 100 may be subsequently assembledwith a cylinder, a stem, and/or any other component(s) of an actuator.

FIG. 4 is an enlarged, cross-sectional view of the example piston ring110 of FIGS. 1-3. In the illustrated example, the piston 100 issubstantially disk-shaped and the first portion 308 of the piston ring110 is a first o-ring 400, and the second portion 310 of the piston ring110 is a second o-ring 402. In other examples, the piston 100 is othershapes (e.g., rectangular, triangular, hexagonal, oblong, etc.) and thefirst portion 308 and the second portion 310 of the piston ring 110 areshaped (e.g., rectangularly, triangularly, etc.) to substantiallyconform to the shape of the piston 100. In the illustrated example, thefirst o-ring 400 is in contact with the second o-ring 402 to operativelycouple the first o-ring 400 to the second o-ring 402. The first o-ring400 and the second o-ring 402 illustrated in FIG. 4 are substantiallyconcentric. In some examples, the first portion 308 and the secondportion 310 of the piston ring 110 are integral (e.g., the piston ring110 is a single o-ring or other element). In other examples, the pistonring 110 includes three or more discrete o-rings. In the illustratedexample, the first o-ring 400 has a first cross-sectional size (e.g., across-sectional diameter) and the second o-ring 402 has a secondcross-sectional size smaller than the first cross-sectional size. Thefirst o-ring 400 and/or the second o-ring 402 may have any suitablecross-sectional shape (e.g., circular, hexagonal, rectangular, etc.).

The example first o-ring 400 is disposed between the first end portion106 and the second end portion 108 of the piston 100 adjacent the groove202. In the illustrated example, the first o-ring 400 and the secondo-ring 402 have rounded cross-sectional shapes and the piston 100defines the fluid chamber 200 having substantially right-angled corners404 and 406 adjacent the groove 202. As a result, the piston ring 110and the first end portion 106 of the piston 100 define a second area 408in the fluid chamber 200 adjacent one of the corners 404. The pistonring 110 and the second end portion 108 of the piston 100 define a thirdarea 410 in the fluid chamber 200 between the piston ring 110 and otherone of the corners 406.

In some examples, fluid is substantially removed from (e.g., drained,released, flowed out of, etc.) the second area 408 and/or the third area410. Thus, pressures in the second area 408 and/or the third area 410may be substantially atmospheric. In some examples, fluid may fill someor all of the second area 408 and/or the third area 410. Thus, the fluidmay be disposed in the fluid chamber 200 on the inner diameter side 316of the first o-ring 400 and on an outer diameter side 412 of the firsto-ring 400. Pressures of the fluid in the second area 408 and the thirdarea 410 are less than the first pressure of the fluid in the first area314 to provide a pressure differential across the first o-ring 400. Inthe illustrated example, a first relief valve 414 is disposed in a thirdport 416 defined by the first end portion 106 of the piston 100. Thefirst relief valve 414 is in fluid communication with the second area408 to control the fluid pressure in the second area 408. A secondrelief valve 418 is disposed in a fourth port 420 defined by the secondend portion 108 of the piston 100. The second relief valve 418 is influid communication with the third area 410 to control the fluidpressure in the third area 410. In some examples, the first relief valve414 and/or the second relief valve 418 are in communication with alowest pressure area of the cylinder 102 (e.g., an area in the cylinder302 including fluid that is not employed to drive the piston 100). As aresult of the pressure differential between the first area 314 and thesecond and third areas 408 and 410, force applied by the fluid in thefirst area 314 to the first o-ring 400 is transferred to the secondo-ring 402. When the force is applied to the second o-ring 402, thesecond o-ring 402 applies the force to the wall 312 of the cylinder 302to form the fluid seal against the wall 312 of the cylinder 302. Becausethe cross-sectional size of the second o-ring 402 is smaller than thecross-sectional size of the first o-ring 400, the second o-ring 402applies a second pressure to the wall 312 of the cylinder 302 greaterthan the first pressure applied to the first o-ring 400 via the fluid inthe first area 314.

The value of second pressure is a function of the pressure differentialacross the first o-ring 400, the cross-sectional size of the firsto-ring 400, and the cross-sectional size of the second o-ring 402. Thus,the first pressure, pressures in the second area 408 and the third area410 and/or dimensions of the piston ring 110 may be chosen to enable thepiston ring 110 to apply a desired value of the second pressure againstthe cylinder wall 312. In some examples, the desired value of the secondpressure is a minimum pressure to form the fluid seal (“a sealingpressure”) against the cylinder wall 312 via the second o-ring 402.Thus, the pressure differential across the first o-ring 400 and/or thedimensions of the piston ring 110 may be chosen so that the secondpressure substantially equals the sealing pressure, thereby minimizingwear to the piston ring 110 due to the second pressure of the secondo-ring 402 against the wall 312 of the cylinder 302. In other examples,the pressure differential and/or the dimensions of the piston ring 110may be chosen so that the second pressure is greater than the sealingpressure.

FIG. 5 illustrates another example technique to pressurize the chamber200 of the example piston 100. In the illustrated example, the firstarea 314 is pressurized via fluid 500 from a fluid reservoir 502disposed outside of the cylinder 302. In the illustrated example, thepiston 100 does not include the first check valve 322 and/or the secondcheck valve 324. The fluid 500 may be flowed into the first area 314 viaa conduit 504 (e.g., a flowline, hose, etc.) in fluid communication withthe first area 314 and the fluid reservoir 502. In the illustratedexample, the conduit 504 is directed from the fluid reservoir 502 to thepiston 100 via the first stem 304. The fluid 500 in the fluid reservoir502 may be flowed (e.g., pumped) into the first area 314 and/orpressurized to increase the first pressure inside the first area 314. Insome examples, a pressure of the fluid 500 in the fluid reservoir 502 ismonitored via a pressure sensor 506 in communication with the fluidreservoir 502. Thus, by controlling the flow of the fluid 500 into thefirst area 314 from the fluid reservoir 502 and/or by controlling thepressure of the fluid 500 in the fluid reservoir 502, the first pressurein the first area 314 may be controlled during operation.

Although certain example methods, apparatus and articles of manufacturehave been described herein, the scope of coverage of this patent is notlimited thereto. Such examples are intended to be non-limitingillustrative examples. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe appended claims either literally or under the doctrine ofequivalents.

The Abstract at the end of this disclosure is provided to comply with 37C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature ofthe technical disclosure. It is submitted with the understanding that itwill not be used to interpret or limit the scope or meaning of theclaims.

What is claimed is:
 1. An apparatus comprising: a piston defining achamber and a circumferential groove in communication with the chamber,at least a portion of the chamber to be substantially filled with afluid; and a piston ring disposed in the chamber and the groove, whereinthe fluid is to apply a first pressure to the piston ring to enable thepiston ring to apply a second pressure to a cylinder wall, the secondpressure greater than the first pressure, the piston ring comprises afirst o-ring operatively coupled to a second o-ring, the first o-ring isin contact with the second o-ring.
 2. The apparatus of claim 1, furthercomprising a valve in fluid communication with the chamber.
 3. Theapparatus of claim 2, wherein the valve includes at least one of a checkvalve or a relief valve.
 4. An apparatus comprising: a piston defining achamber and a circumferential groove in communication with the chamber,at least a portion of the chamber to be substantially filled with afluid; and a piston ring disposed in the chamber and the groove, whereinthe fluid is to apply a first pressure to the piston ring to enable thepiston ring to apply a second pressure to a cylinder wall, the secondpressure greater than the first pressure, the piston ring comprises afirst o-ring operatively coupled to a second o-ring, the first o-ringhas a first size and the second o-ring has a second size less than thefirst size, the first o-ring to be disposed in the chamber, the secondo-ring to be disposed in the groove.
 5. The apparatus of claim 4,further comprising a valve in fluid communication with the chamber. 6.An apparatus comprising: a piston defining a chamber and acircumferential groove in communication with the chamber, at least aportion of the chamber to be substantially filled with a fluid; and apiston ring disposed in the chamber and the groove, wherein the fluid isto apply a first pressure to the piston ring to enable the piston ringto apply a second pressure to a cylinder wall, the second pressuregreater than the first pressure, the piston ring comprises a firstportion having a first size and a second portion having a second sizeless than the first size.
 7. The apparatus of claim 6, wherein thepiston ring comprises a first o-ring operatively coupled to a secondo-ring.
 8. The apparatus of claim 6, further comprising a valve in fluidcommunication with the chamber.
 9. An apparatus comprising: a pistondefining a chamber and a circumferential groove in communication withthe chamber, at least a portion of the chamber to be substantiallyfilled with a fluid; and a piston ring disposed in the chamber and thegroove, wherein the fluid is to apply a first pressure to the pistonring to enable the piston ring to apply a second pressure to a cylinderwall, the second pressure greater than the first pressure, wherein thepiston ring is to form a fluid seal against the piston to enable thefluid in a first portion of the chamber to have the first pressure andthe fluid in a second portion of the chamber to have a third pressureless than the first pressure.
 10. The apparatus of claim 9, wherein thepiston ring comprises a first o-ring operatively coupled to a secondo-ring.
 11. The apparatus of claim 9, further comprising a valve influid communication with the chamber.
 12. An apparatus, comprising: apiston defining a fluid chamber and a circumferential groove incommunication with the fluid chamber; a first seal disposed in the fluidchamber; and a second seal disposed in the groove and operativelycoupled to the first seal, wherein the first seal is to provide a fluidseal against the piston, and the second seal is to provide a fluid sealagainst a cylinder wall.
 13. The apparatus of claim 12, wherein thefirst seal comprises a first o-ring, and the second seal comprises asecond o-ring.
 14. The apparatus of claim 13, wherein the first o-ringis in contact with the second o-ring.
 15. The apparatus of claim 12,wherein a fluid in the fluid chamber is to have a first pressure on afirst side of the first seal and a second pressure on a second side ofthe first seal, the first pressure greater than the second pressure. 16.The apparatus of claim 12 further comprising a relief valve in fluidcommunication with the fluid chamber.
 17. The apparatus of claim 12,wherein the first seal has a first size, and the second seal has asecond size smaller than the first size.
 18. The apparatus of claim 12,wherein the piston comprises a first end portion coupled to a second endportion via a spacer.
 19. An apparatus comprising: a piston including afirst end portion spaced apart from a second end portion to define afluid chamber; and a piston ring disposed between the first end portionand the second end portion of the piston to define a first area in thefluid chamber and a second area in the fluid chamber, the first area tobe substantially filled with a fluid, wherein a first portion of thepiston ring is to form a fluid seal against the first end portion of thepiston and the second end portion of the piston, and a second portion ofthe piston ring is to form a fluid seal against a cylinder wall, whereinthe first portion of the piston ring has a first size and the secondportion of the piston ring has a second size smaller than the firstsize.
 20. The apparatus of claim 19, wherein the piston defines acircumferential groove, and the second portion of the piston ring isdisposed in the groove.
 21. An apparatus comprising: a piston includinga first end portion spaced apart from a second end portion to define afluid chamber; and a piston ring disposed between the first end portionand the second end portion of the piston to define a first area in thefluid chamber and a second area in the fluid chamber, the first area tobe substantially filled with a fluid, wherein a first portion of thepiston ring is to form a fluid seal against the first end portion of thepiston and the second end portion of the piston, and a second portion ofthe piston ring is to form a fluid seal against a cylinder wall, whereina pressure differential is to be provided across the first portion ofthe piston ring.
 22. The apparatus of claim 21, wherein the pistondefines a circumferential groove, and the second portion of the pistonring is disposed in the groove.
 23. An apparatus comprising: a pistonincluding a first end portion spaced apart from a second end portion todefine a fluid chamber; a piston ring disposed between the first endportion and the second end portion of the piston to define a first areain the fluid chamber and a second area in the fluid chamber, the firstarea to be substantially filled with a fluid, wherein a first portion ofthe piston ring is to form a fluid seal against the first end portion ofthe piston and the second end portion of the piston, and a secondportion of the piston ring is to form a fluid seal against a cylinderwall; and a relief valve in communication with the second area of fluidchamber.
 24. The apparatus of claim 23, wherein the piston defines acircumferential groove, and the second portion of the piston ring isdisposed in the groove.